Carbon arrangements for highintensity electric arcs



July 26, 1960 J. A. PERRIN 2, 4

CARBON ARRANGEMENTS FOR HIGH-INTENSITY ELECTRIC ARCS Filed May 17, 1956In venlar Fig.4 F gg- Fig-7 Y Mire.

United States Patent CARBON ARRANGEMENTS FOR HIGH- INTENSITY ELECTRICARCS Jean Adrien Peri-in, Pagny-sur-Moselle, France, assignor to Societele Carbonate-Lorraine, Paris, France Filed May 17, 1956, Ser. No.585,421

4 Claims. (Cl. 313-231 The present invention relates to a device whichcan be applied to the cathodes of very high intensity electric arcswhich exceed 500 amperes for instance, so that these arcs may bestabilised and that advantage can be taken of their high light output.

The form of the arc plasma between carbon or graphite electrodes changesin accordance with the electrical intensity. In the range of the smallintensities, say from a few amperes to 80 amperes, the part situatednear the cathode contracts. At about 80 amperes, there appears a smallvein emanating from the cathode spot. When 1 the intensity is increased,this vein becomes more precisely outlined, grows taut and is surroundedwith coaxial gaseous sheaths, and the cathode part of the discharge,from approximately one hundred amperes onwards, looks like a sheaf whichhas several zones and does not seem to be influenced by the currentintensity. This special form of the discharges, in particular with anintensity of approximately 200 amperes, is sometimes referred to as acontracted column and is well-known and has been described by a numberof authors. However, when certain higher intensities are reached, whichdepend on the nature of the cathode and the functioning conditions, thecathode column changes abruptly; its aspect becomes blurred andhomogeneous, its volume increases, the central vein and the sheathswhich surround it disappear, the arc becomes very noisy, whilst itsoperation is disturbed in an annoying manner: the vapours emitted by theanode are dispersed, and the current partly encroaches on the peripheryof the crater whose depth decreases. Brilliancy diminishes to a largeextent. Ger- 1 man authors have established that the temperature of thecathode spot then reaches that of carbon sublimation at atmosphericpressure.

The present invention has for its object substantially to remove thesedrawbacks through a suitable cooling of 1 the cathode. This is obtainedby utilizing a special cathode current input which has the followingcharacteristics: (1) A hollow current input head placed very near to(approximately 2 cm. from) the extremity of the cathode. (2) An internalcooling of the current input head by means of a circulation fluid. Theinternal cooling fluid is preferably a liquid (water for instance), butit can also be a gas (air for instance). V

(3) The blowing of a gas in order to press back positive vapours and todecrease their radiation on the cathode; the gas for pressing back canbe atmospheric air.

The form of the hollow current input head for the cathode carbon avoidsthe striking of a parasitic are between the cathode head and thecathode. This head is made of metal, preferably a very good electricityand heat conductor, such as silver or copper. The inside ofv the head ishollowed out, and has two apertures through which the cooling fluidflows in and out respectively.

The gas blowing tube is provided with an aperture whose main dimensionsare unequal. The gas jet which comes out of it thus forms a sheet whichis preferably given a large dimension which is approximately equal tothe diameter of the flow of anode vapours which is to be pressedback, i

pointing in opposite directions.

2,946,913 Patented Jul 26, 1 960 "ice tube are united into one singlepart, it is preferable to tilt the gaseous sheet, andthus the outletaperture or apertures of the tube, towards the cathode axis, whichenables the current input head to have suitably reduced. dimensions. Itis prefer-red that the gas inlet jet be situated above the zone wherethe cathode and anode flames meet.

The invention will be better understood with reference to theaccompanying figures. Taking an arc of from 600 to 650 amperes as anon-limiting example, the various forms indicated hereunder have beenestablished.

Figure 1 represents a mounting comprising: a positive carbon 1 of 24 mm.diameter and normally taking an intensity of 450 amperes, inclined bydegrees to the positive carbon axis.

A negative carbon 2 whose diameter is 18 mm., basically having an outerlayer graphited in the mass, provided with a wick whose diameter is 2.5mm., and whose composition, which is moreover variable within certainlimits, remains independent from the characterising features of theinvention. According to this device the current input head and theblowing tube are independent from each other.

Figure 2 shows the shape of the outlet aperture of the blowing tube.

Figure 3 represents a modification according to which the current inputhead and the blowing tube are assembled to form one single part.

Figures 4, 5, 6 and 7 show schematically some modifications of thedevice of Figure 3.

With reference to Figures 1 and 2 the and signs indicate the anode andthe cathode respectively. The cathode is supported by the metallic head3, internally hollowed out in channels or in a chamber (not shown)intended for the circulation of the cooling fluid.

In order to simplify the drawing, these various parts have not beenshown. The cathode 2 can slide with an easy fit.

' The'blowing tube is represented by 4; it is made for instance of a.cylindrical tube whose inlet aperture is shown at 5; the outlet zone isflattened in such a manner that the blown gas comes out as anapproximately plane sheet and that the terminal aperture has the shapeshown in plan in Figure 2. The elongation 'of this aperture is thusperpendicular to the plane of Figure 1. The anode flames 7 and thecathode flames 6 meet and mix in the zone situated between the axis ofthe cathode and the median plane of the blowing tube, a plane whosetrace 8, 9 can be seen on the top right hand side of Figure 1.

In Figure 3 the anode and the cathode are disposed as in Figure l. Thecurrent input head 13 which is constructed in the same way as thecorresponding head 3 of Figure 1, forms a single body with the blowingtube 14. i At the bottom the circulation of the cooling fluid has beenshown schematically by means of two parallel arrows A channel 14situated at the upper part, receives the blowing gas from the bottom,said gas flowing through the internal passage in the direction of thearrow 15 and coming out atthe' upper. part. Whereas the gas inlet at theside'of arrow I; 15. single, .the outlet 16.is arranged so as to producethe almost plane sheet of the outflow gas. To that effect, this outletaperture has been made according to one of the devices shownschematically in Figures 4, 5, 6, 7, by way'of example. These figuresshowthe single part .13, 1450f Figure 3 as it looks when it is examined:facing the tip of the cathode.

In'Figure 4, the cathode slides in the central aperture 22.: It. hasbeen represented as a circle,but any section whatsoever can be made inorder to fit exactly thestraight section of the cathode, the latterbeingforinstance elliptical, rectangular or square. The cathode head 23is pierced atthe upper part of the aperture 24 of .the blowing gas.In'this embodiment, the gaseous sheet flowing out is no longer almostplane but. is slightly curved inwardly which does not impair itsefiicie'ncy.

Figure 5 differs from the preceding drawings only in the rectilinearshape of the blowing aperture. 34; the cathode-bearing channel 32 andthe cathode head 33 are again'seen on it.

According to Figures 6 and 7, instead of usinga single and continuoussheet of blowing gas, the latter is made to flow out through a number ofdiflerent'apertures 46,

In the latter figures the arrangement has the advantage,

thanks to internal lay-out of the ducts extending from the inletaperture to each of the outlet apertures, that the outlet speeds at thevarious apertures may be made unequal and that each of the jets may bedirected at will, these being all parallel to the cathode axis, or beingmore or less tilted towards this axis,'thus enabling a more eflicientblowing at the place where it is most needed, generally through theaxial aperture 46. The number and the dimensions of these apertures canmoreover vary. If they are present in odd numbers, the median apertureis generally speaking, placed on top of the device; if they are in evennumbers, the median part remains full and the apertures aresymmetrically in relation tothe vertical plane passing through thecathode axis.

As far as the directions taken by the gaseous flow in coming out of theapertures 46 is concerned, it is preferred that they be substantiallyparallel. It is not, however, a necessary condition. It is for instance,possible to tilt somewhat the axes of the ducts 46 in order to give someslight convergence to the various individual flows and to facilitate orimprove the desired cooling.

Figures 4, 5, 6, 7 can relate to a special method of cooling the cathodehead wherein the fluid projected on the anode flame also helps to cooldown this head. The heads 23, 33, 43, 53 are provided with theirrespective channels 22, 32, 42, 52, as previously. The apertures 24, 34,46, 54 and 57 allow the escape, towards the anode, of the fluid injectedin the head which is cooled at the same time as the Walls of thechannels 22, 32, 42, 52.

The use of a single part consisting of a cooled cathodebearer andblowing tube can be effected either by making the various ducts andnecessary cavities in one piece from a metallic mass, or by constructingseparately the two devices which are finally assembled, for instance, bywelding them together.

Example By way of a non-limiting example which can serve as anindication, the feeding of an arc of from 600 to 650 amperes will bedescribed. The anode has a thick wick and its diameter is 24 mm.; thecathode has a small wick, with a graphite outer-layer, its diametermeasuring 18 mm. the wick being about 2.5 mm. The angle of the two axesof these carbons is 135. The cathode support is, ofthe. type of Figure 1being .cooled bymeans of water circulation; the distance 18 between thecathode tip and the front face of its support is on the average 17 mm.The distance between the axis of the tube 4 and that of the cathode is50 mm. The blowing gas is atmospheric air. Under these conditions thearcs functioning is maintained regular and without any disturbance atall current intensities, up to- 650 amperes approximately. However, itsuffices to stop the blowing for the cathode flame to become blurred asfrom 475 amperes onwards approximately which proves the efficiency ofthe device.

The use of thevarious modifications described has led to the samefindings; the stability of the arc has always persisted during theblowing, up to current intensities which are very much higher than thosewhich are possible when the blowing is stopped.

In the. foregoing description it will be clear that a carbon arrangementis provided wherein blowing means is carried by and asymmetricallylocated with respect to the negative carbon.

It should be also stressed that the cooling of the cathode tip isobtained according to the invention by acting at one and the same timethrough heat exchanges between the cathode-bearer and the cathode,through calorific convection produced by blowing, and through decreaseof the radiation coming from the anode flame, each time under the effectof the blowing. Each of these means is favorable but only theirassociation has made it possible to reach a stable functioning up to thecurrent intensities indicated.

I claim:

1. A carbon. arrangement for high-intensity electric arcs comprising apositive carbon, a negative carbon, said carbons being. non-coaxiallyarranged but with their axes meeting at the positive carbon, and ablowing tube located adjacent said negative carbon and running parallelto said negative carbon for part of its length, said blowing tube beingbent away from said negative carbon and having an outlet for blowing gasin front of and above said positive carbon.

2. A carbon arrangement for high-intensity electric arcs comprising apositive carbon, a negative carbon, said carbons being non-coaxiallyarranged but with their axes meeting at the positive carbon, and ablowing tube located adjacent said negative carbon and running parallelto said negative carbon for part of its length, said blowing tube beingbent away from said negative carbon and being formed with a flat outletaperture for blowing gas in front of and above said positive carbon.

3. A carbon arrangement for high-intensity electric arcs comprising apositive carbon, a negative carbon, said carbons being non-coaxiallyarranged but with their axes meeting at the positive carbon, a blowingtube located adjacent said negative carbon and running parallel to saidnegative carbon for part of its length, said blowing tube being bentaway from said negative carbon and being formed with a curvilinearoutlet aperture for blowing gas in front of and above said positivecarbon.

4. A carbon arrangement for high-intensity electric arcs comprising apositive carbon, a negative carbon, said carbons being non-coaxiallyarranged but with their axes. meeting at the positive carbon, a blowingtube arrangement located adjacent said negative carbon and runningparallel to said negative carbon for part of its length, said blowingtube being bent away from said negative carbonand being formed with aplurality of outlet apertures for blowing gas in front of and above saidpositive carbon.

References Cited in the file of this patent UNITED STATES PATENTS1,995,144 Crocker Mar. 19, 1935 2,063,249 Hansell Dec. 8, 1936 2,105,463Cordes Jan. 18, 1938 2,540,256 Gretener Feb. 6, 1951 2,788,459 GretenerApr. 9, 1957

